1. Field of the Invention
The present invention relates to electromagnetic relays, and in particular electromagnetic relays having a high contact rating and having a central movable contact which makes and breaks with two opposed stationary contacts.
2. Description of the Prior Art
Electromagnetic relays in which an armature and yoke assembly is actuated by an electromagnetic coil and plunger system are known in the art, as described in German Offenlegungsschrift No. 2,728,509. It is a problem in the design of relays of this type to eliminate or substantially minimize current leakage paths between the contact elements of the relay and any connections to ground. This design problem becomes more acute as the switching currents with which the relay is to be used increase. A particularly difficult leakage path to eliminate is that which results from the yoke which must necessarily engage both the magnetic system and at least one of the contacts.
One solution to the problem in the past has been simply to increase the size of the relay, thus increasing all internal distances thereby increasing the resistance and insulating properties of whatever gas is utilized to fill the interior of the relay. Evacuation of the interior of the relay is also utilized, however, if the relay is subjected to a substantial shock the vacuum seal is frequently broken, and the seal will generally deteriorate even in the absence of shock after a period of use.
A further solution is described in German Offenlegungsschrift No. 2,728,509 in which a central movable contact element is provided with an extension which engages a slidable element movable by the magnetic system. This structure, however, results in a relatively poor efficiency of the magnetic system and is thus not completely satisfactory.